This invention relates to compressor systems, and more particularly to air compressor systems.
Prior art air compressors typically include a compressor, a motor to drive the compressor and a coolant system to cool the air discharged by the compressor and the components of the compressor. The compressor generally compresses air to pressures above normal atmospheric pressures. The coolant system includes a cooler and a bypass valve. In some prior art arrangements, the bypass valve is a temperature sensitive thermal valve. FIG. 5 illustrates a prior art thermal bypass valve 10 in a non-actuated position, in which coolant, normally oil, bypasses the cooler. FIG. 6 illustrates the thermal bypass valve in the actuated position, in which coolant is directed to the cooler.
In FIGS. 5 and 6, the valve 10 has an inlet 14 from the coolant system, an outlet 18 to the coolant system, a cooler exit 22, and a cooler return 26. The cooler is a heat exchanger that cools the coolant. The valve 10 includes a spool 30 and a wax cartridge 34 interconnected to the spool 30. The wax cartridge 34 is directly exposed to the coolant flow from the inlet in both the non-actuated position (FIG. 5) and the actuated position (FIG. 6). The wax cartridge 34 senses the inlet fluid temperature of the coolant. In the non-actuated position illustrated in FIG. 5, the coolant flow enters the valve 10 through the inlet 14, and exits through the outlet 18. The valve 10 is generally in the non-actuated position when the inlet fluid temperature is below a predetermined level. As the inlet fluid temperature increases above a predetermined level, the wax cartridge 34 expands and actuates the valve 10 to the actuated position, illustrated in FIG. 6. When the valve 10 is in the actuated position, the coolant flow enters the valve 10 through the inlet 14, exits the valve 10 through the cooler exit 22, flows through the cooler, reenters the valve 10 through the cooler return 26, and exits the valve 10 through the outlet 18. In both the actuated (FIG. 6) and non-actuated positions (FIG. 5), the wax cartridge 34 is directly exposed to the coolant flow from the inlet 14. The wax cartridge 34 senses the inlet fluid flow, and the temperature of the inlet coolant flow influences the wax cartridge 34 when the spool 30 is in both the actuated and non-actuated position.
The temperature of the inlet fluid flow is relatively unstable and fluctuates over a range of temperatures. As the inlet temperature fluctuates up and down, the wax cartridge senses the inlet fluid temperature and moves the spool 30 back and forth between the actuated position and the non-actuated position. This fluctuation of the inlet temperature and movement of the spool 30 is undesirable and creates additional wear and tear on the components of the valve 10, and inconsistent fluid flow through the cooler. Additionally, the fluctuation of the inlet temperature creates an inconsistent outlet temperature.
The invention provides a thermal valve for a compressor system wherein the wax cartridge senses the temperature of the inlet fluid flow only when the spool is in the non-actuated position. The wax cartridge does not sense the temperature of the inlet fluid flow when the spool is in the actuated position. The wax cartridge senses the temperature of the outlet fluid flow when the valve is in the actuated position. The temperature of the outlet fluid flow from the cooler is relatively stable, and does not fluctuate as much as the inlet fluid temperature.